Danfoss VLT Refrigeration Drive FC 103 Programming Manual page 148

Parameter Description
The frequency converter includes functions for detecting if
the load conditions in the system allow the motor to be
stopped:
•
Low-power detection.
•
Low-speed detection.
3 3
No-flow detection
This function is used for detecting a no-flow situation in compressor systems where all valves can be closed. Can be used
both when controlled by the integrated PI controller in the frequency converter or an external PI controller. Program the
actual configuration in parameter 1-00 Configuration Mode.
Configuration mode for
•
Integrated PI controller: Closed loop.
•
External PI controller: Open loop.
NOTICE
Carry out no-flow tuning before setting the PI controller parameters.
Table 3.19 No-flow Detection
No-flow detection is based on the measurement of speed and power. For a certain speed, the frequency converter calculates
the power at no-flow.
This coherence is based on the adjustment of 2 sets of speed and associated power at no-flow. Monitoring power enables
detection of no-flow conditions in systems with fluctuating suction pressure, or of the compressor having a flat charac-
teristic towards low speed.
Base the 2 sets of data on measurement of power at approximately 50% and 85% of maximum speed with the valves
closed. The data is programmed in parameter group 22-3* No-Flow Power Tuning. It is also possible to run a [0] Low Power
Auto Set Up (parameter 22-20 Low Power Auto Set-up) automatically stepping through the commissioning process and storing
the data measured. Set the frequency converter for [0] Open Loop in parameter 1-00 Configuration Mode, when carrying out
the auto set-up, see parameter group 22-3* No-Flow Power Tuning No-flow Power Tuning.
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VLT Refrigeration Drive FC 103
One of these 2 signals must be active for a set time
(parameter 22-24 No-Flow Delay) before selected action
takes place. Possible actions to select (parameter 22-23 No-
Flow Function):
•
•
•
•
Head
1
2
No action
Warning
Alarm
Sleep mode
Flow
MG16H202